Gear pump device

ABSTRACT

In the present invention, polishing lines  71   f  are connected to an outer circumferential high-pressure region, but are not connected to each area that is a low-pressure region. In this configuration, the polishing lines  71   f  are connected to the outer circumferential high-pressure region where there is high discharge pressure, so high-pressure brake fluid is introduced within the polishing lines  71   f . Therefore, a pushback effect is obtained, wherein gear pumps  19  and  39  are pushed back on the basis of the high-pressure brake fluid pressure. Furthermore, the polishing lines  71   f  are connected to the outer circumferential high-pressure region but are not connected to each area that is a low-pressure region, so high-pressure can be maintained within the polishing lines  71   f , and a reduction in the pushback effect can be prevented. Accordingly, a decrease in the loss torque reduction effect can be prevented, and the loss torque can be further reduced.

TECHNICAL FIELD

The present invention relates to a gear pump device such as a trochoid pump for pumping a fluid by meshing of a gear.

BACKGROUND ART

Conventionally, in a gear pump device, To apply a sealing method using a seal member made of a resin or the like for both end surfaces in the axial direction of the gear pump is a factor of an increase in cost, a structure in which a mechanical seal is used for one of the end surfaces to reduce costs is proposed. More specifically, only one end surface side of an inner rotor and an outer rotor disposed in the gear pump is sealed with the seal member, and, on the other end surface side, a mechanical seal in which each rotor is directly pressed against a sliding surface of a case housing each rotor is employed.

This mechanical seal is a structure in which a metallic inner rotor and a metallic outer rotor are strongly pressed against a metallic case based on elastic force of a seal member and a pressure of a high-pressure fluid to seal. Therefore, when the loss torques of the outer rotor, the inner rotor, and the sliding surface of the case are large, the pump discharge capability is affected, and the motor size must be disadvantageously increased. In addition, when a portion having a large loss torque of rotation and a portion having a small loss torque of rotation occur on the sliding surfaces between the outer rotor, the inner rotor, and the case, heat is generated in a portion where loss torque is large with high-speed or long-time rotation of the pump. A negative effect on the pump discharge capability due to expansion of this heat generating portion is also conceivable.

Thus, a gear pump device coping with these problems has been proposed in Patent Literature 1. Specifically, a radial polishing line is formed on a sliding surface functioning as a mechanical seal of the case. As a result, the contact area between the sliding surface of the case and the two rotors can be reduced, and supply of fluid to the sliding surface is promoted in order to decrease a friction coefficient. This makes it possible to reduce loss torque.

CITATION LIST Patent Literature

Patent Literature 1: Unexamined Japanese Patent Publication No. 2003-129964

SUMMARY OF THE INVENTION Technical Problems

However, in the gear pump device described in Patent Literature 1, radial polishing lines are formed on the entire surface extending from the outer side of the outer rotor to the inner side of the inner rotor where a shaft is disposed, on the sliding surface of the case. Therefore, a high-pressure region outside the outer rotor and a low-pressure region inside the inner rotor communicate with each other via the polishing lines, and a high-pressure fluid leaks from the high-pressure region to the low-pressure region side. This makes it insufficient to obtain a push back effect of pushing back the elastic force of the seal member from the sliding surface side of the case toward both the rotor sides by the high-pressure fluid in the high-pressure region so as to deteriorate the loss torque reduction effect.

In consideration of the above point, the present invention provides a gear pump device capable of improving the push back effect of pushing back from the sliding surface side of the case toward the both the rotor sides and further reducing loss torque.

Solutions to Problems

In order to achieve the above object, according to an invention described in claim 1, there is provided a gear pump device including: a gear pump which has an outer rotor having an inner tooth portion and an inner rotor meshed with the outer rotor while forming a plurality of void portions and performs a suction/discharge operation of a fluid by rotating the outer rotor and the inner rotor based on rotation of a shaft inserted into a center hole of the inner rotor; a case that forms a housing portion that houses the gear pump; and a sealing mechanism disposed between the case and one of pump shaft direction end faces of the gear pump and, in the gear pump, partitioning a low-pressure side including a suction side sucking a fluid and a periphery of the shaft, and a high-pressure side including a discharge side discharging the fluid and a part of gaps between an outer periphery of the outer rotor and the case, the other end surface of the pump shaft direction end surfaces in the gear pump being brought into contact with a sliding surface of the case based on pressing force of the sealing mechanism to seal a portion between the low-pressure side and the high-pressure side of the gear pump on the end surface, wherein, in the sliding surface, a fluid feeding groove which is made of a line radially extending from the center of the gear pump and in which the fluid in the gap between the outer periphery of the outer rotor and the case, which is the high-pressure side, is fed is formed, and the fluid feeding groove is spaced apart from the center hole and the suction side.

When the fluid feeding groove having such a configuration is formed, a high-pressure fluid is fed into the fluid feeding groove because the fluid feeding groove communicates with the outer peripheral high-pressure region having a high discharge pressure. Therefore, a push back effect of pushing back the gear pump based on the high-pressure fluid can be obtained.

Although the fluid feeding groove communicates with the outer peripheral high-pressure region, the fluid feeding groove does not communicate with each portions serving as a low-pressure region. Therefore, a pressure in the fluid feeding groove can be kept high to make it possible to inhibit the push back effect from being deteriorated. Therefore, the loss torque reduction effect can be prevented from being deteriorated to make it possible to further reduce the loss torque.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a hydraulic circuit of a vehicle brake device 1 to which a gear pump device according to a first embodiment of the present invention is applied.

FIG. 2 is a cross-sectional view of the gear pump device.

FIG. 3 is a cross-sectional view taken along line III-III′ of FIG. 2.

FIG. 4 is a diagram showing a cylinder 71 when viewed from a gear pump 19 or a gear pump 39 side.

FIG. 5 is a diagram showing a relationship between a polishing line 71 f formed in the cylinder 71 and a pressure distribution on sliding surfaces 71 b and 71 c of the cylinder 71 and the like.

FIG. 6 is a diagram showing a cylinder 71 disposed in a gear pump device according to a second embodiment of the present invention when viewed from a gear pump 19 or a gear pump 39 side.

FIG. 7 is a diagram showing the relationship between a polishing line 71 f formed in the cylinder 71 and a pressure distribution on sliding surfaces 71 b and 71 c of the cylinder 71 and the like.

FIG. 8 is a diagram showing a discharge pressure region Ra, a suction pressure region Rb, and an intermediate pressure region Rc in the gear pump device.

FIG. 9 is a diagram showing a pressure distribution between the gear pumps 19 and 39 and the sliding surfaces 71 b and 71 c of the cylinder 71.

FIG. 10 is a diagram showing a cylinder 71 disposed in a gear pump device according to a third embodiment of the present invention when viewed from a gear pump 19 side or a gear pump 39 side.

FIG. 11 is a diagram showing a cylinder 71 disposed in a gear pump device according to a fourth embodiment of the present invention when viewed from a gear pump 19 side or a gear pump 39 side.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention will be described below with reference to the accompanying drawings. In all the following embodiments, the same reference numerals denote the same parts or equivalent parts, respectively, to explain the invention.

First Embodiment

A hydraulic circuit of a vehicle brake device 1 to which a gear pump device according to an embodiment of the present invention is applied will be described with reference to FIG. 1. Although an example in which the vehicle brake device 1 according to the present invention is applied to a vehicle having a hydraulic circuit for front and rear piping will be described here, the vehicle brake device 1 can also be applied to an X piping in which a right front wheel and a left rear wheel use a first piping system and a left front wheel and a right rear wheel use a second piping system.

As shown in FIG. 1, the vehicle brake device 1 includes a brake pedal 11, a booster 12, an M/C 13, W/C 14, 15, 34, and 35, a brake hydraulic pressure control actuator 50. A brake ECU 70 is assembled to the brake hydraulic pressure control actuator 50, and the brake ECU 70 controls braking force generated by the vehicle brake device 1.

The brake pedal 11 is connected to the booster 12 and the M/C 13. When a driver steps on the brake pedal 11, stepping force is boosted by the booster 12 to press master pistons 13 a and 13 b disposed in the M/C 13. As a result, equal M/C pressures are generated in a primary chamber 13 c and a secondary chamber 13 d partitioned by the master pistons 13 a and 13 b. The M/C pressure generated in the M/C 13 is transmitted to each W/C 14, 15, 34, and 35 through the brake hydraulic pressure control actuator 50 constituting a hydraulic pressure passage.

Further, to the M/C 13, a master reservoir 13 e having a passage communicating with the primary chamber 13 c and the secondary chamber 13 d is connected. The master reservoir 13 e supplies a brake fluid into the M/C 13 and reserves an excess brake fluid in the M/C 13.

The brake hydraulic pressure control actuator 50 has a first piping system 50 a and a second piping system 50 b. The first piping system 50 a serves as a rear system controlling brake fluid pressures applied to a rear right wheel RR and a rear left wheel RL, and the second piping system 50 b is a front system controlling brake fluid pressures applied to a front left wheel FL and a front right wheel FR.

Hereinafter, the first and second piping systems 50 a and 50 b will be described. Since the first piping system 50 a and the second piping system 50 b have almost the same configurations, here, the first piping system 50 a will be described, and, with respect to the second piping system 50 b, the first piping system 50 a is referred to.

The first piping system 50 a transmits the above M/C pressure to the W/C 14 disposed in the rear left wheel RL and the W/C 15 disposed in the rear right wheel RR, and includes a pipe line A serving as a main pipe line generating a W/C pressure. The W/C pressure is generated in each of the W/Cs 14 and 15 through the pipe line A, so that braking force is generated.

The pipe line A includes a differential pressure control valve 16 that can control the state in the pipe line A to a communication state and a differential pressure state. A valve position is adjusted such that this differential pressure control valve 16 becomes in the communication state in a normal brake state (operational control is not executed) which generate braking force corresponding to an operation of the brake pedal 11 by a driver. When a current is supplied to a solenoid coil disposed in the differential pressure control valve 16, the valve position is adjusted such that the differential pressure control valve 16 becomes in the differential pressure state in which the larger the current value, the larger the pressure difference. When the differential pressure control valve 16 is in the differential pressure state, a flow of the brake fluid is regulated such that the W/C pressure is higher than the M/C pressure by the pressure difference.

On the W/C 14 and 15 side which is downstream of the differential pressure control valve 16, the pipe line A branches into two pipe lines A1 and A2. The pipe line Al includes a pressure increasing control valve 17 controlling boosting of a brake fluid pressure to the W/C 14, and the pipe line A2 includes a pressure increasing control valve 18 controlling boosting of a brake fluid pressure to the W/C 15.

The pressure increasing control valves 17 and 18 each are constituted by a 2-position electromagnetic valve which can control communication/cutoff states. The pressure increasing control valves 17 and 18 each are of a normal-open type in which the control valves are controlled to be in a communication state in a non-energization state in which no control current flows in the solenoid coils included in the pressure increasing control valves 17 and 18 and controlled to be in a cutoff state in an energization state in which a control current flows in the solenoid coils.

In the pipe line B serving as a pressure reducing pipe line connecting the portions between the pressure increasing control valves 17 and 18 and the W/Cs 14 and 15, respectively in the pipe line A and a pressure regulating reservoir 20, a pressure reducing control valve 21 and a pressure reducing control valve 22 are disposed, respectively. These pressure reducing control valves 21 and 22 each are constituted by a 2-position electromagnetic valve which can control communication/cutoff states, and are of a normal-close type in which the control valves are set in the cutoff state in the non-energization state.

A pipe line C serving as a reflux pipe line is disposed between the pressure regulating reservoir 20 and the pipe line A. In the pipe line C, a self-suction gear pump 19 driven by a motor 60 is disposed such that a brake fluid is sucked or discharged from the pressure regulating reservoir 20 toward the M/C 13 side or the W/C 14 or 15 side.

A pipe line D serving as an auxiliary pipe line is disposed between the pressure regulating reservoir 20 and the M/C 13. The brake fluid is sucked from the M/C 13 through the pipe line D by the gear pump 19 and is discharged to the pipe line A to supply the brake fluid to the W/C 14 side and the W/C 15 side under operation control such as antiskid control or traction control so as to increase a W/C pressure of a target wheel.

On the other hand, as described above, the second piping system 50 b has a configuration which is substantially the same as that of the first piping system 50 a. Specifically, the differential pressure control valve 16 corresponds to a differential pressure control valve 36. The pressure increasing control valves 17 and 18 correspond to pressure increasing control valves 37 and 38, respectively, and the pressure reducing control valves 21 and 22 correspond to pressure reducing control valves 41 and 42, respectively. The pressure regulating reservoir 20 corresponds to a pressure regulating reservoir 40. The gear pump 19 corresponds to a gear pump 39. In addition, the pipe line A, the pipe line B, the pipe line C, and the pipe line D correspond to a pipe line E, a pipe line F, a pipe line G, and a pipe line H, respectively. As described above, the hydraulic circuit of the vehicle brake device 1 is constituted, and the gear pump device is formed by integrating the gear pumps 19 and 39 of the above components. The detailed structure of the gear pump device will be described later.

The brake ECU 70 governs a control system of the vehicle brake device 1, and is configured by a well-known microcomputer including a CPU, a ROM, a RAM, an I/O, and the like. The brake ECU 70 executes processing such as various calculations according to programs stored in a ROM or the like to execute vehicle motion control such as antiskid control. Specifically, the brake ECU 70 calculates various physical quantities based on detection of sensors (not shown), and determines whether or not to execute the vehicle motion control based on the calculation results. When the vehicle motion control is executed, the brake ECU 70 calculates a control amount for a wheel to be controlled, that is, a W/C pressure to be generated in the W/C of the wheel to be controlled. Based on the result, the brake ECU 70 controls the motor 60 for driving each of the control valves 16 to 18, 21, 22, 36 to 38, 41, and 42 and the gear pumps 19 and 39 to control the W/C pressure of the wheel to be controlled, thereby performing the vehicle motion control.

For example, when no pressure is generated in the M/C 13 as in the traction control or the antiskid control, the gear pumps 19 and 39 are driven and the differential pressure control valves 16 and 36 are brought into a differential pressure state. As a result, the brake fluid is supplied to the downstream side of the differential pressure control valves 16 and 36, that is, to the W/C 14, 15, 34, and 35 side through the pipe lines D and H. Then, by appropriately controlling the pressure increasing control valves 17, 18, 37, and 38 and the pressure reducing control valves 21, 22, 41, and 42, the pressure increase/decrease of the W/C pressure of the wheel to be controlled is controlled such that the W/C pressure becomes a desired control amount.

Further, in antiskid brake (ABS) control, the pressure increasing control valves 17, 18, 37, and 38 and the pressure reducing control valves 21, 22, 41, and 42 are appropriately controlled, and an increase/reduce pressure of the W/C pressure is controlled by driving the gear pumps 19 and 39 such that the W/C pressure becomes the desired control amount.

Next, the detailed structure of the gear pump device in the vehicle brake device 1 configured as described above will be described with reference to FIGS. 2 to 5. FIG. 2 shows a state in which a pump main body 100 is assembled to a housing 101 of the brake hydraulic pressure control actuator 50. For example, the pump main body 100 is assembled on the assumption that the vertical directions on the drawing sheet of FIGS. 2 and 3 correspond to the vertical directions of the vehicle.

As described above, the vehicle brake device 1 includes two systems, i.e., the first piping system 50 a and the second piping system 50 b. Therefore, the pump main body 100 includes two gear pumps, i.e., the gear pump 19 for the first piping system 50 a and the gear pump 39 for the second piping system 50 b.

The gear pumps 19 and 39 built in the pump main body 100 are driven by rotating, by the motor 60, a rotating shaft 54 supported by a first bearing 51 and a second bearing 52. The outer shape of the pump main body 100 is constituted by an aluminum cylinder 71 and a plug 72. The first bearing 51 is disposed on the cylinder 71 and the second bearing 52 is disposed on the plug 72.

One end side of the cylinder 71 is press-fitted into the plug 72 in a state where the cylinder 71 and the plug 72 are coaxially arranged to integrate the cylinder 71 and the plug 72 with each other, so that the outer shape of the pump main body 100 is configured. Then, the pump main body 100 is constituted by disposing the gear pumps 19 and 39, various seal members, and the like together with the cylinder 71 and the plug 72.

In this way, the pump main body 100 having an integrated structure is constituted. The integrated pump main body 100 is inserted into a substantially cylindrical concave portion 101 a formed in the housing 101 made of aluminum from the right side on the drawing sheet. A ring-shaped male screw member (screw) 102 is screwed into a female thread groove 101 b dug in an entrance of the concave portion 101 a to fix the pump main body 100 to the housing 101. The male screw member 102 is screwed to achieve a structure in which the pump main body 100 does not come off from the housing 101.

In this manner, the pump main body 100 is fixed to the housing 101 to configure a gear pump device. A case of the gear pump device is constituted by the cylinder 71, the plug 72, and the housing 101, and the gear pumps 19 and 39 are housed in the case.

In this specification, a direction of insertion of the pump main body 100 into the concave portion 101 a of the housing 101 is simply referred to as an insertion direction. Further, the axial directions and the circumferential directions of the pump main body 100 and the gear pumps 19 and 39, in other words, pump axis directions and pump axis circumferential directions which coincide with the axial direction and the circumferential direction of the rotating shaft 54 are simply referred to as axial directions and circumferential directions.

A circular second concave portion 101 c is formed at a forward distal end position of the concave portion 101 a in the insertion direction, that is, at a position corresponding to the distal end (the left side end portion in FIG. 2) of the rotating shaft 54 in the bottom portion of the concave portion 101 a. The diameter of the second concave portion 101 c is made larger than the diameter of the rotating shaft 54. The distal end of the rotating shaft 54 is positioned in the second concave portion 101 c to prevent the rotating shaft 54 from coming into contact with the housing 101.

Center holes 71 a and 72 a are disposed in the cylinder 71 and the plug 72, respectively. The rotating shaft 54 is inserted into the center holes 71 a and 72 a and supported by the first bearing 51 fixed to the inner periphery of the center hole 71 a of the cylinder 71 and the second bearing 52 fixed to the inner periphery of the center hole 72 a of the plug 72.

Gear pumps 19 and 39 are disposed on both sides of the first bearing 51, that is, in a region in front of the first bearing 51 in the insertion direction and in a region sandwiched between the first and second bearings 51 and 52, respectively.

As shown in FIG. 3, the gear pump 19 is disposed in a rotor chamber (housing portion) 100 a configured by a concave portion obtained by circularly concaving one end surface of the cylinder 71. The gear pump 19 is configured by an internal-contact-type gear pump (trochoid pump) driven by the rotating shaft 54 inserted into the rotor chamber 100 a.

More specifically, the gear pump 19 includes a rotating portion including an outer rotor 19 a having an inner tooth portion formed on the inner periphery thereof and an inner rotor 19 b having an outer tooth portion formed on the outer periphery thereof, and the rotating shaft 54 is inserted into a center hole 19 ba of the inner rotor 19 b. A key 54 b is fitted into a hole 54 a formed in the rotating shaft 54, and torque is transmitted to the inner rotor 19 b by this key 54 b.

The outer rotor 19 a and the inner rotor 19 b form a plurality of void portions 19 c by meshing the inner tooth portion and the outer tooth portion formed in the outer rotor 19 a and the inner rotor 19 b, respectively, with each other. Then, when the rotating shaft 54 rotates to change the void portions 19 c in size so as to suck and discharge the brake fluid.

On the other hand, as shown in FIG. 2, the gear pump 39 is disposed in a rotor chamber (housing portion) 100 b configured by a concave portion obtained by circularly concaving the other end surface of the cylinder 71 and driven by the rotating shaft 54 inserted into the rotor chamber 100 b. Like the gear pump 19, the gear pump 39 also includes an outer rotor 39 a and an inner rotor 39 b, and the rotating shaft 54 is inserted into a center hole 39 ba of the inner rotor 39 b. The gear pump 39 is configured by an internal-contact-type gear pump which sucks and discharges a brake fluid with a plurality of void portions 39 c formed by meshing both the teeth portions of the respective rotors 39 a and 39 b. The gear pump 39 is disposed such that the gear pump 19 is rotated by about 180 degrees about the rotating shaft 54. When the gear pump 39 is disposed in this way, the void portions 19 c and 39 c on the suction side of the gear pumps 19 and 39 and the void portions 19 c and 39 c on the discharge side are made symmetrical with respect to the rotating shaft 54 to make it possible to cancel out force applied to the first bearing 51 by a high-pressure brake fluid pressure on the discharge side.

These gear pumps 19 and 39 basically have the same structures, respectively. In the embodiment, a polishing line 71 f (see FIGS. 4 and 5) formed on sliding surfaces 71 b and 71 c of the cylinders 71 constituting a part of the cases of the gear pumps 19 and 39 is changed from the conventional one. In this way, loss torque is reduced. Details of the structure of the polishing line 71 f will be described later.

On one end surface side of the cylinder 71, a sealing mechanism 111 pressing the gear pump 19 toward the cylinder 71 side is disposed on an opposite side to the cylinder 71 with the gear pump 19 interposed therebetween, that is, between the cylinder 71, the gear pump 19, and the housing 101. Further, on the other end surface side of the cylinder 71, on the side opposite to the cylinder 71 with the gear pump 39 interposed therebetween, that is, between the cylinder 71, the gear pump 39, and the plug 72, a sealing mechanism 115 pressing the gear pump 39 toward the cylinder 71 side is disposed.

The sealing mechanism 111 is constituted by a ring-shaped member having a hollow portion into which the rotating shaft 54 is inserted. This sealing mechanism 111 presses the outer rotor 19 a and the inner rotor 19 b toward the cylinder 71 side to seal a relatively low-pressure part and a relatively high-pressure part on the one end surface side of the gear pump 19. More specifically, the sealing mechanism 111 exerts a sealing function by bringing the bottom surface of the concave portion 101 a serving as an outer contour of the housing 101 and desired positions of the outer rotor 19 a and the inner rotor 19 b.

In the embodiment, the sealing mechanism 111 is configured to include an inner member 112 having a hollow frame shape, an annular rubber member 113, and an outer member 114 having a hollow frame shape. The inner member 112 is fitted into the outer member 114 in a state in which the annular rubber member 113 is disposed between an outer peripheral wall of the inner member 112 and an inner peripheral wall of the outer member 114.

In addition, the outer diameter of the sealing mechanism 111 is made smaller than the inner diameter of the concave portion 101 a of the housing 101 at least on the upper side on the drawing sheet of FIG. 2. Therefore, in this configuration, the brake fluid can flow through the gap between the sealing mechanism 111 and the concave portion 101 a of the housing 101 on the upper side on the drawing sheet. This gap constitutes a discharge chamber 80 and is connected to a discharge pipe line 90 formed on the bottom of the concave portion 101 a of the housing 101. With such a structure, the gear pump 19 can discharge the brake fluid by using the discharge chamber 80 and the discharge pipe line 90 as discharge paths. In an operation of the pump 19, the outer member 114 is pressed toward the gear pump 19 side by a high-pressure discharge side brake fluid pressure so that the sealing performance of the one end surface of the gear pump 19 by the sealing mechanism 111 is further secured.

Further, in the cylinder 71, a suction port 81 which communicates with the void portions 19 c on the suction side of the gear pump 19 is formed. The suction port 81 extends from the end surface of the cylinder 71 on the gear pump 19 side to the outer peripheral surface and is connected to a suction pipe line 91 disposed on the side surface of the concave portion 101 a of the housing 101. As shown in FIGS. 2 and 4, a suction groove 71 d causing the center hole 71 a and the suction port 81 to communicate with each other is formed in an end surface of the cylinder 71 on the gear pump 19 side. With such a structure, the gear pump 19 can feed the brake fluid by using the suction pipe line 91 and the suction port 81 as suction paths.

On the other hand, the sealing mechanism 115 is also formed of a ring-shaped member having a central portion into which the rotating shaft 54 is inserted. By the sealing mechanism 115, the outer rotor 39 a and the inner rotor 39 b are pressed toward the cylinder 71 side to seal a relatively low-pressure part and a relatively high-pressure part on the one end surface side of the gear pump 39. More specifically, the sealing mechanism 115 exerts a sealing function by contacting the end surface of the portion of the plug 72 in which the sealing mechanism 115 is housed, and the desired position of the outer rotor 39 a and the inner rotor 39 b.

The sealing mechanism 115 is also configured to include an inner member 116 having a hollow frame shape, an annular rubber member 117, and an outer member 118 having a hollow frame shape. The inner member 116 is fitted into the outer member 118 in a state in which the annular rubber member 117 is disposed between the outer peripheral wall of the inner member 116 and the inner peripheral wall of the outer member 118.

This sealing mechanism 115 has the same basic structure as the sealing mechanism 111. However, since the surface constituting the seal of the sealing mechanism 111 and the surface constituting the seal of the sealing mechanism 115 are opposite to each other, the structures are made different from each other accordingly. More specifically, the sealing mechanism 115 has a structure which is symmetrical to that of the sealing mechanism 111, and the sealing mechanism 115 is disposed with a phase shifted by 180° with respect to the sealing mechanism 111 around the rotating shaft 54. Other than that, the sealing mechanism 115 has the same structure as that of the sealing mechanism 111.

Note that the outer diameter of the sealing mechanism 115 is smaller than the inner diameter of the plug 72 at least on the lower side on the drawing sheet. Therefore, the brake fluid can flow through the gap between the sealing mechanism 115 and the plug 72 on the lower side on the drawing sheet. This gap constitutes a discharge chamber 82 and is connected to a discharge pipe line 92 formed in a communication passage 72 b formed in the plug 72 and on the side surface of the concave portion 101 a of the housing 101. With such a structure, the gear pump 39 can discharge the brake fluid by using the discharge chamber 82, the communication passage 72 b, and the discharge pipe line 92 as discharge paths. In an operation of the pump 39, the outer member 118 is pressed toward the gear pump 39 side by the high-pressure discharge side brake fluid pressure so that the sealing performance of the one end surface of the gear pump 39 by the sealing mechanism 115 is further secured.

On the other hand, the gear pumps 19 and 39 are brought into contact with the sliding surfaces 71 b and 71 c, in which the end surfaces of the cylinders 71 on the gear pumps 19 and 39 sides also function as sealing surfaces, that is, the surfaces on which the rotors 19 a, 19 b, 39 a, and 39 b are slid to achieve sealing (mechanical seal). As a result, a relatively low-pressure part and a relatively high-pressure part on the other end surface sides of the gear pumps 19 and 39 are sealed.

A suction port 83 communicating with the void portion 39 c on the suction side of the gear pump 39 is formed in the cylinder 71. The suction port 83 extends from the end surface of the cylinder 71 on the gear pump 39 side to the outer peripheral face and is connected to a suction pipe line 93 disposed on the side surface of the concave portion 101 a of the housing 101. With such a structure, the gear pump 39 can feed the brake fluid by using the suction pipe line 93 and the suction port 83 as suction paths.

In FIG. 2, the suction pipe line 91 and the discharge pipe line 90 correspond to the pipe line C in FIG. 1, and the suction pipe line 93 and the discharge pipe line 92 correspond to the pipe line G in FIG. 1.

At the rear of the first bearing 51 in the insertion direction in the center hole 71 a of the cylinder 71, a seal member 120 including an annular resin member 120 a having a U-shaped section in the radial direction and an annular rubber member 120 b fitted in the annular resin member 120 a is housed. The seal member 120 seals the two systems in the center hole 71 a of the cylinder 71.

The center hole 72 a of the plug 72 has a stepped shape in which the inner diameter is reduced in three steps from the front to the rear in the insertion direction, and a seal member 121 is housed in the first stepped portion which is on the rearmost side in the insertion direction. The seal member 121 is formed by fitting a ring-shaped elastic ring 121 a made of an elastic material such as rubber into a ring-shaped resin member 121 b having a groove portion whose depth direction is the radial direction, and the seal member 121 is brought into contact with the rotating shaft 54 by pressing the resin member 121 b with elastic force of the elastic ring 121 a.

Note that the sealing mechanism 115 described above is housed in the second stepped portion which is the step next to the step in which the seal member 121 is disposed, of the center hole 72 a. The communication passage 72 b described above is formed to extend from the stepped portion to the outer peripheral surface of the plug 72. An end portion of the cylinder 71 on the rear side in the insertion direction is press-fitted into the third stepped portion which is on the frontmost side in the insertion direction, of the center hole 72 a. A portion of the cylinder 71 fitted into the center hole 72 a of the plug 72 has an outer diameter smaller than that of the other portion of the cylinder 71. Since the axial dimension of the reduced-diameter portion of the cylinder 71 is made larger than the axial dimension of the third stepped portion of the center hole 72 a, when the cylinder 71 is press-fitted in the center hole 72 a of the plug 72, a groove portion 74 c by the cylinder 71 and the plug 72 is formed at the distal end position of the plug 72.

Further, the diameter of the center hole 72 a of the plug 72 is partially increased even at the rear in the insertion direction, and an oil seal (seal member) 122 is disposed in this portion. In this way, by disposing the oil seal 122 on the motor 60 side with respect to the seal member 121, basically, the seal member 121 prevents a brake fluid from leaking to the outside through the center hole 72 a to make it possible to more reliably obtain the effect by the oil seal 122.

O-rings 73 a to 73 d serving as annular seal members are disposed on the outer periphery of the pump main body 100 configured as described above so as to seal the respective parts. The O-rings 73 a to 73 d seal the brake fluid between two systems formed in the housing 101 and between the discharge path and the suction path in each system. The O-ring 73 a is disposed between the discharge chamber 80 and the discharge pipe line 90, and the suction port 81 and the suction pipe line 91. The O-ring 73 b is disposed between the suction port 81 and the suction pipe line 91, and the suction port 83 and the suction pipe line 93. The O-ring 73 c is disposed between the suction port 83 and the suction pipe line 93, and the discharge chamber 82 and the discharge pipe line 92. The O ring 73 d is disposed between the discharge chamber 82 and the discharge pipe line 92, and the outside of the housing 101. The O-rings 73 a, 73 c, and 73 d are simply arranged in a circular shape to surround the circumferential direction around the rotating shaft 54. However, although the O-ring 73 b surrounds the circumferential direction around the rotating shaft 54, the O-ring 73 b is disposed to be shifted in the axial direction to make it possible to reduce the dimension in the axial direction of the rotating shaft 54.

Groove portions 74 a to 74 d are formed in the outer periphery of the pump main body 100 so that the O-rings 73 a to 73 d can be arranged. The groove portions 74 a and 74 b are formed by partially concaving the outer periphery of the cylinder 71. The groove portion 74 c is formed by a concaved portion of the outer periphery of the cylinder 71 and a distal portion of the plug 72. The concave portion 74 d is formed by partially concaving the outer periphery of the plug 72. When the pump main body 100 is inserted into the concave portion 101 a of the housing 101 in such a state that the O-rings 73 a to 73 d are fitted in the groove portions 74 a to 74 d, respectively, the O-rings 73 a to 73 d are flattened out on the inner wall surface of the concave portion 101 a and function as a seal.

Further, the outer peripheral surface of the plug 72 is reduced in diameter at the rear in the insertion direction to constitute the stepped portion. The above ring-shaped male screw member 102 is fitted in the reduced diameter portion so as to fix the pump main body 100.

The gear pump device is constituted by the structure as described above. Next, the detailed structures of the sliding surfaces 71 b and 71 c of the cylinder 71 constituting a part of the cases of the above gear pumps 19 and 39 will be described. Since the sliding surfaces 71 b and 71 c have the same configurations, both the sliding surfaces 71 b and 71 c are shown as being the same in FIGS. 4 and 5.

The sliding surfaces 71 b and 71 c as shown in FIGS. 4 and 5 are constituted by end surfaces of the cylinder 71 on the side opposite to the sealing mechanisms 111 and 115 with the gear pumps 19 and 39 interposed therebetween. Specifically, the center hole 71 a is formed at a center position of the end surface, and discharge grooves 71 e placed at positions corresponding to the suction ports 81 and 83 and the discharge chambers 80 and 82 are formed on both sides of the center hole 71 a. Portions except for the center hole 71 a, the suction port 81, and the discharge groove 71 e on the end face constitute sliding surfaces 71 b and 71 c on which both the rotors 19 a, 19 b, 39 a, and 39 b slide when the gear pumps 19 and 39 are driven.

In the sliding surfaces 71 b and 71 c, the polishing lines 71 f constituting fluid feeding grooves are formed. The polishing lines 71 f are formed by, for example, polishing. In the embodiment, the plurality of polishing lines 71 f are formed to extend radially from the centers of the gear pumps 19 and 39. Here, the centers of the gear pumps 19 and 39 are set as the center of the center hole 71 a, but the polishing lines 71 f need only be formed radially with respect to the center hole 71 a, and a specific position need not be set as the center.

The plurality of polishing lines 71 f are caused to communicate with portions of the rotor chambers 100 a and 100 b outside the outer rotors 19 a and 39 a (to be referred to as outer peripheral high-pressure region hereinafter). The plurality of polishing lines 71 f are prevented from communicating with the center hole 71 a, the suction ports 81 and 83, and the suction groove 71 d in which the portion of the polishing lines 71 f communicating with the outer peripheral high-pressure region becomes the low-pressure region. In the case of the embodiment, the inner peripheral side ends of the plurality of polishing lines 71 f are separated from the center hole 71 a, the suction ports 81 and 83, and the suction groove 71 d.

As described above, the polishing lines 71 f are formed on the sliding surfaces 71 b and 71 c of the cylinder 71.

When the polishing lines 71 f each having such a configuration are formed, since the polishing lines 71 f are in communication with the outer peripheral high-pressure region in which the polishing lines 71 f have a high discharge pressure, a high-pressure brake fluid is fed into the polishing lines 71 f. Therefore, a push back effect that pushes the gear pumps 19 and 39 back based on the high brake fluid pressure. Even if the polishing lined 71 f are caused to communicate with the outer peripheral high-pressure region, the polishing lines 71 f are not caused to communicate with each part serving as the low-pressure region. Therefore, the inside of the polishing lines 71 f can be kept at a high pressure to make it possible to inhibit the push back effect from being deteriorated. Therefore, the loss torque reduction effect can be prevented from being deteriorated to make it possible to further reduce the loss torque.

Second Embodiment

A second embodiment of the present invention will be described below. This embodiment is obtained by modifying the polishing lines 71 f with respect to the first embodiment, and the other parts are the same as those of the first embodiment, so that only the difference from the first embodiment will be described.

As shown in FIGS. 6 and 7, in the embodiment, while a plurality of polishing lines 71 f are formed to extend radially from the centers of the gear pumps 19 and 39, a low-pressure portion 71 fa capable of communicating with the low-pressure void portions 19 c and 39 c of the polishing lines 71 f is separated from a high-pressure portion 71 fb which is caused to communicate with the outer peripheral high-pressure region on an outer peripheral side of the low-pressure portion 71 fa.

Specifically, the fluid pressures of the respective parts in the gear pumps 19 and 39 are shown in FIG. 8, and a high-pressure region Ra into which a discharge pressure is fed, a low-pressure region Rb into which a suction pressure is fed, and an intermediate pressure region Rc into which an intermediate pressure between these pressures is fed are present. The pressures between the gear pumps 19 and 39 and the sliding surfaces 71 b and 71 c of the cylinder 71 are shown in FIG. 9. Therefore, based on the pressure relationships shown in FIGS. 8 and 9, the low-pressure portion 71 fa is formed in a range including the low-pressure region Rb, and the high-pressure portion 71 fb is not formed in the low-pressure region Rb.

As shown in FIG. 8, the suction ports 81 and 83, the suction grooves 71 d, and the center hole 71 a have low pressures. When the void portions 19 c and 39 c communicate with the suction ports 81 and 83 and the suction grooves 71 d, and, further, until the void portions 19 c and 39 c increase in volume after communicating therewith, the void portions 19 c and 39 c are in a low-pressure state. For this reason, in the polishing lines 71 f, a place which can communicate with the void portions 19 c and 39 c in the low-pressure state is defined as the low-pressure portion 71 fa, a place which communicates with gaps between the outer peripheries of the outer rotors 19 a and 39 a in a high-pressure state and the cylinder 71 is defined as the high-pressure portion 71 fb. The high-pressure portion 71 fa and the low-pressure portion 71 fb are separated from each other.

In other words, no polishing line 71 f is formed in a predetermined region. Specifically, as shown in FIGS. 6 and 8, in the void portions 19 c and 39 c, in a range in which confinement portions 19 d and 39 d which each become the intermediate pressure region Rc with which neither the high-pressure region Ra nor the low-pressure region Rb of the void portions 19 c and 39 c is in communication are located, no polishing line 71 f is formed. That is, no polishing line 71 f is formed in a range of passing tracks of the confinement portions 19 d and 39 d. In addition, no polishing line 71 f is formed in the range along the movement locus of the void portions 19 c and 39 c on the outer peripheral side of the region where the void portions 19 c and 39 c are in a low-pressure state.

The confinement portions 19 d and 39 d mentioned here mean those of the void portions 19 c and 39 c the volumes of which become maximum. More specifically, in the rotational directions of the gear pumps 19 and 39, the gaps 19 c and 39 c have volumes which are maximum until the void portions 19 c and 39 c move from a part communicating with the suction ports 81 and 83 to a part communicating with the discharge chambers 80 and 82, and the void portions 19 c and 39 c the volumes of which are maximum are called the confinement portions 19 d and 39 d.

Incidentally, the void portions 19 c and 39 c also have confinement portions 19 e and 39 e obtained when the volumes become minimum, but the confinement portions 19 e and 39 e communicate with the low-pressure portion 71 fa of the polishing lines 71 f. Since the volumes of the confinement portions 19 e and 39 e are small, an influence of pressure fluctuation or the like is small even if the confinement portions 19 e and 39 e communicate with the low-pressure portion 71 fa. Therefore, although the low-pressure portion 71 fa is caused to communicate with the confinement portions 19 e and 39 e, no polishing line 71 f may be formed also in this region.

In this manner, the polishing lines 71 f may be configured to separate the low-pressure portion 71 fa caused to communicate with the low-pressure region Rb such as the suction ports 81 and 83 from the high-pressure portion 71 fb caused to communicate with the high-pressure region Ra such as the discharge chambers 80 and 82. In this way, a high-pressure fluid can be inhibited from leaking from a higher-pressure region to a low-pressure region side. Therefore, the loss torque reduction effect can be prevented from being deteriorated to make it possible to further reduce the loss torque.

Third Embodiment

A third embodiment of the present invention will be described below. This embodiment is obtained by modifying the polishing lines 71 f of the second embodiment, and the other parts are the same as those of the second embodiment, so that only the difference from the second embodiment will be described.

As shown in FIG. 10, in the embodiment, the polishing lines 71 f are constituted by radial curves extending from the centers of the gear pumps 19 and 39. The low-pressure portion 71 fa and the high-pressure portion 71 fb of each of the polishing lines 71 f are arranged such that the intermediate position thereof is located in front of both the end portions in the rotational direction of the gear pumps 19 and 39. That is, the low-pressure portion 71 fa and the high-pressure portion 71 fb are curved to form a convex shape so that the convex portion faces forward in the rotational direction.

In this way, when the low-pressure portion 71 fa and the high-pressure portion 71 fb are constituted by radial curves, the portion curved in rotation of the gear pumps 19 and 39 plays the role of a wedge to prevent the brake fluid fed into the interior from flowing in the inner circumferential direction. Therefore, the brake fluid in the polishing lines 71 f is difficult to be drawn from the high-pressure region to the low-pressure region side to make it possible to maintain the high-pressure state of the polishing lines 71 f. As a result, the loss torque reduction effect can be further prevented from being deteriorated to make it possible to further reduce the loss torque.

Fourth Embodiment

A fourth embodiment of the present invention will be described below. This embodiment is obtained by modifying the polishing lines 71 f with respect to the first embodiment, and the other parts are the same as those of the first embodiment, so that only the difference from the first embodiment will be described.

As shown in FIG. 11, in this embodiment, a virtual circle C indicated by a dashed line in the drawing is set at the center position of each of the gear pumps 19 and 39, and the polishing lines 71 f are disposed to extend in the tangential direction of the virtual circle C. Specifically, the polishing lines 71 f are formed such that the end portions on the inner peripheral sides of the gear pumps 19 and 39, of the polishing lines 71 f are located in front of the end portions on the outer peripheral sides in the rotational direction. The size of the virtual circle C is arbitrary, and is, for example, made equal to or smaller than the diameter of the center hole 71 a.

In this manner, even in a layout in which the polishing lines 71 f extend in the tangential direction with respect to the virtual circle C, the same effect as that in the first embodiment can be obtained. The polishing lines 71 f are disposed such that the end portions on the inner peripheral sides of the gear pumps 19 and 39, of the polishing lines 71 f are positioned in front of the end portions on the outer peripheral sides in the rotational direction. For this reason, based on the rotational motions of the gear pumps 19 and 39, the brake fluid flowing in from the end portion on the outer peripheral side becomes easy to flow to the end portion on the inner peripheral side. Therefore, a high-pressure state can be easily secured over the entire area of the polishing lines 71 f, and the effect described in the first embodiment can be more easily obtained.

Another Embodiment

The present invention is not limited to the above embodiments, and can be arbitrarily changed and modified without departing from the scope described in claims.

For example, the example in which the radial polishing lines 71 f are disposed as the fluid feeding grooves is described. However, the fluid feeding grooves may be formed by the grooves other than the polishing lines 71 f. For example, the fluid feeding groove may be formed by a laser-processed groove formed by laser processing. When a laser-processed groove is used, since burrs such as those caused by machining do not occur, the influence of the burrs can be eliminated. Further, in the laser processing, since a surface to be processed which is at a deep position can be processed, formation of a fluid feeding groove can also be facilitated.

In each of the above embodiments, a gear pump device having the two gear pumps 19 and 39 each constituted by an internal-contact-type gear pumps is taken as an example. However, a gear pump device in which only one gear pump is employed may be used. Further, in each of the above embodiments, the gear pump device including the two gear pumps 19 and 39 is given, and cases constituting housing portions (rotor chambers 100 a and 100 b) of the gear pumps 19 and 39 are constituted by the housing 101, the cylinder 71, and the plug 72. However, this is merely an example. For example, the case may be constituted by only a thing which constitutes the outer shape of the pump main body 100.

In addition, although the suction groove 71 d is formed in one end surface of the cylinder 71, a structure which does not include the suction groove 71 d may be employed. In that case, the polishing lines 71 f are preferably formed also on the portion where the suction groove 71 d is located. 

1. A gear pump device comprising: a gear pump which has an outer rotor having an inner tooth portion and an inner rotor meshed with the outer rotor while forming a plurality of void portions and performs a suction/discharge operation of a fluid by rotating the outer rotor and the inner rotor based on rotation of a shaft inserted into a center hole of the inner rotor; a case that forms a housing portion that houses the gear pump; and a sealing mechanism disposed between the case and one of pump shaft direction end surfaces of the gear pump and, in the gear pump, partitioning a low-pressure side including a suction side sucking a fluid and a periphery of the shaft, and a high-pressure side including a discharge side discharging the fluid and a part of gaps between an outer periphery of the outer rotor and the case, the other end surface of the pump shaft direction end surfaces in the gear pump being brought into contact with a sliding surface of the case based on pressing force of the sealing mechanism to seal a portion between the low-pressure side and the high-pressure side of the gear pump on the end surface, wherein, in the sliding surface, a fluid feeding groove which is made of a line radially extending from the center of the gear pump and in which the fluid in the gap between the outer periphery of the outer rotor and the case, which is on the high-pressure side, is fed is formed, and the fluid feeding groove is spaced apart from the center hole and the suction side.
 2. The gear pump device according to claim 1, wherein the fluid feeding groove is not formed in a range in which a confinement portion having a maximum volume is located among the plurality of void portions.
 3. The gear pump device according to claim 1, wherein of the plurality of void portions, the fluid feeding groove has a portion formed at a place where the fluid feeding groove communicates with, a void portion caused to communicate with the suction side and being in a low-pressure state as a low-pressure portion, and a place communicating with a gap between the outer periphery of the outer rotor being in a high-pressure state and the case as a high-pressure portion, and the low-pressure portion and the high-pressure portion are separated from each other.
 4. The gear pump device according to claim 1, wherein the fluid feeding grooves are constituted by radial curves, and an intermediate position located between both ends of each of the fluid feeding grooves is located in front of the gear pump in a rotational direction of the gear pump.
 5. The gear pump according to claim 1, wherein the fluid feeding groove is formed in a radial shape which extends in a tangential direction of a virtual circle which is set at a center position of the gear pump.
 6. The gear pump device according to claim 5, wherein the fluid feeding groove is formed such that, of the fluid feeding groove, an and portion on an inner peripheral side of the gear pump is more forward than an end portion on an outer peripheral side in the rotational direction of the gear pump.
 7. The gear pump device according to claim 2, wherein of the plurality of void portions, the fluid feeding groove has a portion formed at a place where the fluid feeding groove communicates with, a void portion caused to communicate with the suction side and being in a low-pressure state as a low-pressure portion, and a place communicating with a gap between the outer periphery of the outer rotor being in a high-pressure state and the case as a high-pressure portion, and the low-pressure portion and the high-pressure portion are separated from each other.
 8. The gear pump device according to claim 2, wherein the fluid feeding grooves are constituted by radial curves, and an intermediate position located between both ends of each of the fluid feeding grooves is located in front of the gear pump in a rotational direction of the gear pump.
 9. The gear pump device according to claim 3, wherein the fluid feeding grooves are constituted by radial curves, and an intermediate position located between both ends of each of the fluid feeding grooves is located in front of the gear pump in a rotational direction of the gear pump.
 10. The gear pump according to claim 2, wherein the fluid feeding groove is formed in a radial shape which extends in a tangential direction of a virtual circle which is set at a center position of the gear pump.
 11. The gear pump according to claim 3, wherein the fluid feeding groove is formed in a radial shape which extends in a tangential direction of a virtual circle which is set at a center position of the gear pump.
 12. The gear pump device according to claim 10, wherein the fluid feeding groove is formed such that, of the fluid feeding groove, an and portion on an inner peripheral side of the gear pump is more forward than an end portion on an outer peripheral side in the rotational direction of the gear pump.
 13. The gear pump device according to claim 11, wherein the fluid feeding groove is formed such that, of the fluid feeding groove, an and portion on an inner peripheral side of the gear pump is more forward than an end portion on an outer peripheral side in the rotational direction of the gear pump. 